An FM-CW radar has the ease of configuration and a relatively low frequency of the baseband that facilitates signal processing, and is thus used commonly these days as a millimeter wave band collision avoidance radar or the like with the aim of reducing cost.
An FM-CW scheme uses an up-chirp signal that varies a transmit frequency from a low frequency to a high frequency and a down-chirp signal that varies the frequency from a high frequency to a low frequency, and calculates the distance to a target as well as relative velocity with respect to the target on the basis of a sum of peak frequencies and a difference in the peak frequencies of beat signals respectively obtained from the chirp signals.
On the other hand, transmit/receive modules making up the FM-CW radar require adjustment work in a delivery inspection process due to individual differences and temperature characteristics of voltage control oscillators (hereinafter noted as a “VCO”), and thus hinder reduction of the inspection time in mass production. Because no feedback control performed after shipment, there is a problem in that the radar is unable to respond to a change in the characteristics of the VCO caused by aging or the like.
Note that Patent Literature 1 discloses the configuration including: a frequency divider that divides, by the number of divisions N, an output signal from the VCO an oscillating frequency of which varies according to an analog control voltage; a digital phase detector that detects phase information from an output signal of the frequency divider and outputs digital phase information; and a differentiator that differentiates the digital phase information output from the digital phase detector and converts the information into digital frequency information.